Electrophotographic method of making an imaging master

ABSTRACT

An imaging system capable of making a plurality of prints from a single master is provided wherein an electrostatic latent image is developed with a liquid developer comprising an insulating carrier liquid having dispersed therein finely divided dyeabsorbing particles and finely divided colored pigment to provide a colored dye-absorbing toner image. The dye-absorbing toner image is fixed to the imaging surface to provide an imaging master. A print may be obtained by first contacting the master with a dye solution and finally contacting it with a dye receiving layer to produce a final colored image on the dye receiving layer.

United States Patent Tamai 1 1 Feb. 4, 1975 [54] ELECTROPHOTOGRAPHIC METHOD OF 3,677,766 7/1972 Tam ai et 111. 96/1 LY MAKING AN IMAGING MASTER 3,692,523 9/1972 Tumai et a1. 96/1 LY X 3,718,593 Z/1973 Tamai 252/6211 Inventor: Yasuo Tamal, Asaka, Japan 3,738,832 6/1973, Matsumoto et a1 96/12 1731 Assam Xerox Corporation, Rochester 31213? 151333 $233;3211;331:1111: 313211 E [22] Filed: Oct. 29, 1973 OTHER PUBLICATIONS [2]] Appl' 410367 Derwent, Belgium Patents Report No. 22/69, Belgium Related [1.8. Application D t Pat. No. 724,581, May 2, 1969, to Fuji Film. [60] Division of Ser, No. 222,268, Jan. 31, 1972, Pat. No. I I I 3,806,339, which is a continuation of Ser. No. 8,415, Primary Examiner-Norman G. Torchm Feb. 3, 1970, abandoned. Assistant Examiner-J0hn R. Miller [30] Foreign Application Priority Data [57] ABSTRACT Feb. 10, 1969 Japan 44-9968 An g g system capable of making a plurality of prints from a single master is provided wherein an [52] US 96/1 96/12 electrostatic latent image is developed with a liquid 51 1111.0. G03g 13/10, G03g 13/22 fieveloper F l i 9" [58] Field of Search 96/1 LY l 117/37 LB mg d1spersedthere1nf1nely d1v1ded dye-absorbing par- 252/62 1 ticles and finely divided colored pigment to provide a colored dye-absorbing toner image. The dye-absorbing [56] References Cited toner image is fixed to the imaging surface to provide an imaging master. A print may be obtained by first UNITED STATES PATENTS contacting the master with a dye solution and finally 3,236,639 2/1966 Tomanekw contacting it with a dye receiving layer to produce a 3,444,083 5/1969 Ol1phant 252/621 final comred image on the dye receiving lay, 3,622,515 11/1971 Tama1etal.... 252/621 3,654,865 4/1972 Tamai 252/621 4 Claims, N0 Drawings ELECTROPIIOTOGRAPI-IIC METHOD OF MAKING AN IMAGING MASTER This is a divisional of application Ser. No. 222,268, filed Jan. 31, 1972, now U.S. Pat. No. 3,806,339, which is a continuation of application Ser. No. 8,4l5, filed Feb. 3, 1970, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to imaging systems and more particularly to imaging systems employing liquid development and liquid developers for developing an electrostatic latent image. More specifically, this invention relates to improvements in liquid developers having incorporated therein a gelatin toner to be used in a repro duction process which converts an electrostatic latent image into gelatin image which sequentially absorbs a colored dye and transfers the dye from the gelatin matrix to a receiver sheet. I

Two processes are widely known for producing color prints of good quality. The most popular process for the reproduction of a multicolor image is carried out through the use of light sensitive material having multiple coated silver halide emulsion layers which are subjected to a color development method. I

The other process is the dye transfer process whereby gelatin matrixes are produced by developing exposed halogenated silver emulsion layers with a tanning developer. The gelatin relief image is contacted with a dye and absorbs the dye. Upon subsequent contact with a receiver surface, the dye is transferred in image configuration. A representative commercial application of this process is known as the Technicolor" process. The former process is suitable for volume processing. However, the image to be obtained has insufficient durability against light irradication. In contrast, the dye transfer process can produce images of good quality having extremely high durability. However, it is not suited to produce a small number of prints from a single original since it requires a rather complex procedure with an experienced hand to prepare the gelatin matrixes which serve as master plates for dye transfer printing which increases the cost per print. For this reason, this process offers improved economy when it is used for producing many duplicates from one original.

Recently, a simplified method of rapidly, easily and inexpensively producing a master for use in the dye transfer process has been invented. U.S. application Ser. No. 780,495 filed Dec. 2, 1968, now U.S. Pat. No. 3,764,309, discloses this novel color reproduction process, the disclosure of which is hereby incorporated by reference. Therein described is a technique of producing multicolored prints of excellent quality in color and which are light fast and which comprises the following steps:

I. An electrostatic latent image is formed on the photoconductive insulating layer of an electrophoto graphic recording member or on the insulating coating of an electrostatic recording member.

2. The electrostatic latent image is converted into a toner image which is composed of a material, gelatin, for example, which is capable of readily absorbing an aqueous solution of a water-soluble dye.

3. The resultant toner image is fixed by a suitable method.

4. Dye imbibition into the toner image is obtained by contacting the toner image with an aqueous solution of a water-soluble dye, to allow the image to absorb the dye.

5. A separately prepared element having a surface capable of readily absorbing the dye is so positioned that the dye-receiving layer thereof comes into contact with the aforementioned toner image and the dye transfers onto the dye-receiving layer producing the final image on the element.

In this process, however, since the toner layer is substantially colorless and transparent, evaluation of the quality of the image cannot be made until the toner image has been contacted with the colored dye solu tion. This difficulty is particularly noticeable when the toner image is placed on ordinary electrophotographic sensitive paper since the surface of such paper is coarse and has a white to very slight color making it very difficult to recognize the toner layer. As a result, it is difficult to adequately adjust the extent of charging. exposure and development until after virtually all steps in the process are completed.

SUMMARY OF THE INVENTION It is therefore an object of the invention to provide a developing system which overcomes the above noted deficiencies.

It is another object of the invention to provide a novel liquid developer.

It is another object of the invention to provide an improved methodof color reproduction in a dye transfer process.

It is another object of the invention to provide a dye transfer matrix discernible by color from the imagin surface.

It is another object of the invention to provide an improved liquid developing agent for use in the preparation of the gelatin matrix.

The above objects and others are accomplished, generally speaking, by providing an imaging system employing a liquid developer comprising an insulating carrier liquid having dispersed therein finely divided dye absorbing particles and finely divided colored pigment. With such a developer the image formed in response to the electrostatic latent image from the dye absorbing material has the color of the colored pigment and evaluation of the adequacy of electric charging exposure, and development is readily immediately ascertained without having to contact the dye absorbing image with a dye.

Typically, the procedure of the aforementioned color printing process by using the liquid developing agent of this invention is as follows:

1. An electrostatic latent image is formed on a suitable imaging surface such as electrophotographic sensitive layer which is electrically charged in the dark and exposed to light through an image.

2. The sensitive layer carrying thereon the electrostatic latent image is treated with the liquid developer of the present invention comprising dye absorbent toner material and colored pigment dispersed in the carrier insulating liquid, to develop the latent image.

3. The resultant dye absorbing toner image is fixed and hardened by any suitable method. Since the toner image thus obtained has a color, visual evaluation of the quality of the image can be performed at this stage. In other words, it is possible to examine the image to determine whether or not the electric charging, exposure, and development have been adequate.

4. The dye absorbent toner image is brought into contact with an aqueous solution of a water-soluble dye, and the image is allowed to absorb the dye.

5. The excess dye solution which adheres to the dye absorbing toner matrix is removed by washing with an acidic cleaning water.

6. A separately prepared sheet having a surface capable of readily absorbing the aforementioned dye is positioned so that the dye-receiving layer comes into contact with the dye absorbing toner image. At this point, the dye transfers to the dye-receiving layer, to form a final color image on the sheet.

A multiplicity of sheets each carrying the dye image can be obtained by repeating steps (4), (5), and (6) with the same dye absorbent toner matrix.

Any suitable well known insulating liquid may be employed as the liquid vehicle for the dye absorbing material and colored pigment particles. Typical well known materials have volume resistivities greater then about 10" ohm-cm so as not to affect the electrostatic charge pattern on the insulating layer. Generally, the insulating liquids have low dielectric constants of less than about 3.4. Typical well known specific vehicles include among others, the nonpolar hydrocarbons and hydrocarbon derivates such as benzene, kerosene, cyclohexane, toluene and carbon tetrachloride.

Any suitable dye absorbing toner material which is insoluble in water and has a strong affinity for a water soluble dye may be employed. Typical materials include gelatin, casein, glue, albumin and other polypeptide polymeric materials.

Any suitable colored pigment particle which is insoluble in the carrier liquid may be employed. Typical colored pigments include carbon black, phthalocyanine blue, Milori blue, iron oxide, permanent red 28, phthalocyanine black, brilliant carmine 6B, diamond black, Watching red, pyrazoline red B, fast sky blue, phthalocyanine green, pigment green B and the like.

The dye absorbing toner material and colored pigment may be employed in any suitable amount. Typically, the colored pigment particles are present in an amount of from about 1% to about by weight of the dye absorbing toner.

The quantity of colored pigment to be contained in the liquid developer of this invention is desired to be as small as possible compared to that of dye absorbing toner. The reason is that the amount of dye absorbing toner allowed to deposit decreases in inverse proportion as the amount of the colored pigment deposited increases. In addition, the colored pigment toner used is preferred to have as deep a color as practical since the quantity of the colored pigment toner added to the liquid developer containing the dye absorbing toner can be proportionally decreased as the color becomes deeper. The pigment toner may be of the type having positive charge or of the type having negative charge. The dye absorbing toner material may have any suitable charge. The gelatin toner, for example, has a positive charge. When a minor amount of negatively charged pigment toner is added to the liquid developer containing gelatin toner, the overall electric charge remains unchanged in polarity. it has been confirmed that in the course of image development, the pigment having a negative charge when present in a small quantity does not behave separately from the gelatin toner having a positive charge when present in a larger quantity. This is most likely because the aforementioned two toners are interlocked with each other within the liquid developer. In consideration of greater storage ability of a liquid developer, however, it is preferred to add a pigment having a positive charge to the gelatin toner as far as practical.

In the liquid developer used in the present invention, the dye absorbing toner and pigment particle may be of any suitable size. Typically, the dye absorbing toner has an average particle diameter not exceeding 5 microns preferably below l micron. The colored pigment toner which is added in a smaller quantity preferably have nearly the same or smaller particle diameter as that of the dye absorbing toner.

As discussed above, the quantity of the colored pigment toner to be added may be of the order of one fifth to one hundredth based on the weight of the dye absorbing toner. When the colored pigment toner is added in a larger quantity, the quantity of dye absorbing toner to be eluted will be reduced relatively as already mentioned, with the consequence that the final color image obtained will have a lower optical density. When the colored pigment toner is added in too small a quantity, the dye absorbent toner image obtained after the step of image development is too low in density and the addition of pigment toner is deprived of its significance.

Gelatin is a particularly preferred dye absorbing material in obtaining good color reproduction. The gelatin toner may be prepared by any following of the procedures:

l A powdery gelatin is mechanically crushed in a wet or dry process. Typically, this crushing may be accomplished in a ball mill, colloid mill, grinder, jet mill, or an attriter such as the wet crushing machine manufactured by Mitsui Miike Machinery Company, Ltd.

2. An aqueous solution of gelatin is added to an organic solvent which is miscible with water but incapable of dissolving gelatin. A dispersion of gelatin is obtained and the gelatin particles are collected.

3. An aqueous solution of gelatin is sprayed into dry air or other gas or into vacuum to obtain gelatin powder.

4. An aqueous solution of gelatin is combined with methanol, ethanol, or the like. The mixture is then added to an organic solvent which is miscible with methanol, ethanol, or the like but incapable of dissolving gelatin. There is consequently obtained a dispersion of gelatin particles. The dispersed gelatin particles are caused to transfer into the carrier liquid.

5. According to the procedure disclosed in my copending application for Letters Patent Ser. No. 8,414, filed concurrently herewith, and now US. Pat. No. 3,755,l77 a gelatin gel is crushed in an organic solvent which is miscible with water but incapable of dissolving gelatin. A dispersion of gelatin particles and the dispersed gelatin particles are collected from the disperston.

The gelatin powder obtained from the above processes is dispersed in the carrier liquid to obtain a liquid developer containing the gelatin toner.

Of the above methods, l) and (3) are useful for the preparation of gelatin toner having a relatively large particle diameter and are suitable for imaging processes directed to obtaining duplicates of line drawings. Methods (2), (4) and (5) are suitable for obtaining gelatin toner having a relatively small particle diameter.

A separately prepared liquid developer containing a colored pigment toner is added to the liquid developer having the gelatin toner therein and the mixture is agitated to produce the developer used in the step of image development in the present invention. Any of the well known methods of preparing liquid developers containing colored pigment toner may be employed. Similarly, processing pigments such as flash colors may be used. It is also possible to have a colored pigment contained in the gelatin toner. In this case, however, it is necessary to have the pigment finely and homogeneously dispersed within the gelatin.

After the toner image is formed, it is fixed to the imaging surface in any suitable manner. Typical satisfactory methods for fixing the toner image to the imaging surface include: thermo fixation wherein the dye absorbing toner image is a thermoplastic material and is softened by the application of heat; solvent fixation wherein a certain solvent softens the toner image; and, steam fixation wherein the application of steam softens or melts and fixes the toner. The toner image may also be fixed by either embedding the image in the surface of the recording layer of by overcoating the image with a suitable resinous material which permits the dye solution to diffuse through a thin film into the toner material.

Typically, any suitable dye may be employed to form the dyed toner image. The dye to be used in the invention is either acidic or mordant. The dye is dissolved in a pH-adjusted distilled water and allowed to be absorbed by the gelatin image.

Typical'Cyan dyes include acid blue 45, acid green l6, acid green 1, acid blue 1, acid blue 9, and acid blue 54 by color index. Typical magenta dyes include acid red 80, acid red 34, acid red 1, acid violet l9, and acid violet 7 by color index. Typical yellow dyes include acid yellow 23, acid yellow ll, direct yellow 12, and acid yellow 34 by color index.

The dye image obtained by the present invention has excellent quality with high resistance to light and excellent color quality. Compared with an image which is obtained by using toners of varying colors electrophotographically, this dye image does not involve surface reflection and therefore reproduces the color with rich depth. Further, since component colors in the dye image are transparent, they are mixed completely to permit faithful reproduction of color.

The dye image which is obtained can produce images on many transfer sheets by the transfer method as long as the dye is replenished. A multiplicity of color prints may, therefore, be produced.

When the colored pigment toner is contained in the liquid developer incorporating therein the dye absorbing toner material as is done by the present invention, regulation of electric charging and exposure necessitated with any change of originals can be accomplished with added ease. This is because the adequacy of charging, exposure and development can be determined through visual observation of the colored dye observing toner image immediately after the image development step without the necessity of having to wait until the final step of dye transfer is completed.

If any difficulty occurs at the time of image development, it may be detected immediately. The present invention therefore eliminates waste and increases the efficiency of operation to a great extent and is accordingly very important from an industrial viewpoint.

Any suitable imaging surface may be employed. Typically, the imaging surface comprises an insulating recording layer capable of retaining an electric charge. It may, for example, be selected from the well known group of dielectric materials and an electrophotographic sensitive layer containing a photoconductive substance and an insulating resin on a waterproof base. In ordinary electrophotographic sensitive materials, a low electric resistant layer is provided between the sensitive layer and the base. The well known photoconductive materials may typically be employed.

When photoconductive zinc oxide is used as the photoconductive substance in the sensitive layer, it is necessary to remove the zinc oxide from within the sensitive layer after development with the dye absorbing material and prior to contact with the dye. This is necessary because the surface of the sensitive layer containing zinc oxide assumes weak basicity upon contact with water and, as a consequence, may impede the absorption of dye by the dye absorbing material. This is particularly true when gelatin is the dye absorbing material. As a further consequence, the dye which is absorbed once is eluted in the step of (5) when excess dye solution is washed away. Accordingly, this step may be very important. An aqueous solution of acid is used for removing the zinc oxide from the photosensitive layer.

It is desirable that aqueous solution exceeding 5% in concentrations of acetic acid, nitric acid, sulfuric acid, hydrochloric acid and the like be used in this step.

The removal of zinc oxide from the sensitive layer carrying the dye absorbing toner image does not result in destruction of the dye absorbing toner image. This is partially true when gelatin is employed as the dye absorbing material. It is noted that the portion carrying the gelatin image enjoys rather higher mechanical stability.

With the exception of the steps of charging and exposure as described in step (I) of the outlined procedure, the remaining steps may be reqularly accomplished by fixing the processing conditions or automating'the procedure. In step (1), a color slide is generally used as the original. By means of filters, trichromatic exposure is performed to obtain three different electrophotographic sensitive papers from the original. For this reason, exposure conditions must be varied each time a new original is used. It is, therefore, desirable to evaluate the adequacy of the charging and exposure at an early stage in the process.

When the liquid developer which contains dye absorbing toner but does not contain a finely divided powder of colored pigment is employed, the evaluation to determine whether or not steps 1) through (5) have been performed satisfactorily can be performed only after step (6). This is because the dye absorbing material and particularly a gelatin toner is substantially colorless and transparent and the surface of an electrophotographic sensitive members such as zinc oxide, is frequently coarse and has a white to very slight color and therefore, when the dye absorbing toner is allowed to deposit on the surface of the sensitive layer, the image can barely be recognized in a whitish shade. By comparison, a selenium plate has a smooth surface and is black in color, and the dye absorbing toner image may be observed since it stands out in a white shade. The image quality can be usually evaluated after development. Even with the use ofa selenium plate, for optimum evaluation of imaging parameters, it is preferred to use the liquid developer containing the colored pigment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS The following preferred examples further define, describe and compare preferred materials, methods and techniques of the present invention. In the examples, all parts and percentages are by weight unless otherwise specified. Example II is presented for comparative purposes.

EXAMPLE I Five grams of photographic gelatin are added to 95 grams of distilled water and permitted to stand for 30 minutes after which the gelatin swells. The gelatin is then heated to 60C. to obtain a clear water solution of gelatin. Ten milliliters of aqueoussolution of gelatin are maintained at 45C., and methanol is added to until a slight shite suspension occurs. About 1 l milliliters of methanol is added. Then 0.5 milliliters of distilled water is added to eliminate the white suspension. A solution of gelatin in a mixed solvent of water and methanol is obtained. This solution is dispersed by means of ultrasonic waves in a liquid of the following composition.

980 ml 20 ml Acetone Cotton seed oil Varnish prepared by heating rosin-modified I 4 ml phcnolformaldehyde resin with linseed oil Toluene 36 ml The resin component within the varnish is insoluble in acetone, but soluble in the carrier liquid.

Upon addition, an aggregate of resin within the liquid immediately formed. After standing for about 30 minutes, the aggregate settled substantially,.and the supernatant is removed by decantation.

Then about 800 milliliters of acetone is added to the sediment and the mixture agitated. After standing for minutes, the supernatant is removed by decantation to obtain about 200 milliliters of liquid containing the sediment. This liquid is treated with a centrifugal separator to obtain a resin sediment containing finely di-' vided gelating particles. The sediment in its entirety is added to a mixed solvent having the following composition and the mixture is agitated:

Toluene ml Xylene 3.5 ml Cotton seed oil 6 ml Nonionic surface active agent solution 0.3 ml

The sediment is substantially completely dissolved by the action of agitation. A rather viscous dispersion of gelatin having a yellowish white color is obtained. This liquid is a concentrated dope of liquid developer and can be preserved unaffected for a long time.

The entire volume of this concentrated dope is poured into a carrier liquid having the following composition:

I600 ml Cyclohexune Kerosene Phthalocyanine blue 5 g Varnish prepared by heating rosin-modified 25 g phenolformaldehyde resin and linseed oil Toluene 30 ml One milliliter of the resultant paste is added to a carrier liquid having the following composition and allowed to disperse therein.

Cyclohexane Kerosene Fifty milliliters of the blue liquid developer are added to 200 milliliters of the aforementioned liquid developer containing the gelatin toner, and the mixture is agitated. A liquid developing agent having a light blue color is obtained.

Separately, IOO parts by weight of photoconductive zinc oxide and 20 parts by weight of epoxy ester of dehydrated castor oil fatty acid are combined with a suitable amount of toluene and converted into a homogeneous coating liquid. To this liquid, 20/1000 part of fluorescein and 20/lOO part of tetrabromophenol blue dissolved in a small amount of ethylene glycol monomethyl ether are added to expand the photosensitivity of zinc oxide to the entire visible spectrum. With a suitable amount of toluene being added, the liquid is spread on a film of polyethylene terephthalate having a thickness of p. upon which aluminum has been vacuum deposited. The dry thickness of the coating is about 8 When this film is dried sufficiently in the dark, it serves satisfactorily as an electrophotographic material. This electrophotographic sensitive material is exposed to negative corona discharge in the dark to uniformly charge its surface. A color slide is mounted as an original on an enlarger, with a red filter fixed on the slide. The negatively charged sensitive material is exposed to light projected through the original and filter.

The exposed sensitive material is wetted with kerosene and, with minimum loss of time, soaked in the above liquid developer contained in a vat made of stainless steel which functions as the developing electrode when the surface of the latent image is brought close to the bottom of vat. After about 90 seconds of soaking in the bath, the sensitive material is removed, washed with isoparaffin (lsopar E available from Humble Oil and Refining Company), and dried.

After development, the sheet is soaked in a 1% methanol solution of formalin, allowed to stand overnight at room temperature, to harden the gelatin image.

A sensitive layer carrying thereon a gelatin image having a light bluish color is obtained.

For the purpose of removing zinc oxide from the sensitive layer, a solution of the following composition is prepared to remove the zinc oxide from the sensitive layer.

40 ml 60 ml The sensitive material carrying the gelatin image is soaked in this solution and the solution is occasionally agitated.

After standing for two minutes, the zinc oxide is removed from the surface of the sensitive layer, so that the entire surface assumes a metallic luster because of the aluminum layer beneath the sensitive layer.

The sheet is then washed sufficiently in distilled water. Finally, the sheet is soaked in a bath of methanol, removed from the bath, and dried in a current of forced hot air. A matrix for cyan printing is thereby obtained.

By the same procedure, another sheet is exposed to light projected through the same original combined with a green filter and subjected to the step of image developement in the same manner to obtain a matrix for magenta printing. Similarly, a matrix for yellow printing is obtained by combining the original with a blue filter. t

The three matrixes are soaked for two minutes in aqueous solutions of acid blue 54. acid violet 7, and acid yellow 23 in color index respectively, removed from the baths, and washed in a cleaning bath of acetic acid.

The dye-receiving element is soaked in aluminum sulfate solution, mordanted, and thereafter registered to and pressed against the three matrixes one after another to allow the dye absorbed in the toner images to be transferred onto the dye receiving element. A duplicate of excellent quality is obtained. One hundred duplicates are made using these matrixes with no alteration in print quality.

EXAMPLE ll The procedure of Example I is repeated except that the liquied developer having the gelatin toner is used without addition thereto of the liquid developer containing the blue pigment. After the step of image development, a white gelatin toner is barely recognized to have been eluted on the sensitive layer which is a slightly greyish color. Visually, this image is quite indistinct. It is impossible to determine the adequacy of the conditions of charging, exposure and image development at this time. The evaluation is of course possible after the step of dye transfer.

EXAMPLE III The procedure of Example I is repeated except that the developer of blue pigment is replaced by a liquid developing agent which is prepared in the following manner. The mixture of the following composition is agitated in a high-speed mixer to obtain a red liquid developer.

Microlith Red a pigment available from Ciba l g Toluene 50 ml Cyclohcxane 50 ml Five milliliters of this red liquid developing agent is added to 2000 milliliters of liquid developing agent containing gelatin toner prepared as described in Example A liquid developing agent containing the gelatin toner and having a light red color is obtained.

The procedure of Example I is followed using this liquid developer. After the step of image development. a gelatin image of light red color, which is in such condition that the adequacy of the conditions of exposure and image development could be determined through visual observation is obtained. Through the same procedure, other gelatin matrixes are obtained.

EXAMPLE IV The procedure of Example l is repeated except the liquid developer of blue pigment is replaced by a liquid developer which is prepared in the following manner. The mixture of the following composition is treated by the ultrasonic wave dispersion process to obtain a liquid developer.

Plano-blue (offset ink made by Fuji Film) 1 g Cyclohexane 200 ml Kerosene 40 ml Ten milliliters of this blue liquid developing agent are added to 200 milliliters of the liquid developer containing the gelatin toner of Example I.

Through the same procedure as Example I, gelatin matrixes of excellent quality are obtained.

EXAMPLE V The procedure of Example I is repeated except that the liquid developer of blue pigment is replaced by the commercially available electrophotographic liquid developer Electron Copister." a black developing agent manufactured by Mita Industrial Co, Ltd.

Forty milliliters of this liquid developing agent are added to 1000 milliliters of the liquid developing agent containing the gelatin toner of Example I.

Gelatin matrixes of excellent quality are obtained through the procedure of Example I.

The technique provided by the instant invention provides a faster, less complicated manner of evaluating the adequacy of image formation and of making an imaging master. It further reduces the time necessary to determine the adequacy of charging, exposure and development in a process capable of making a plurality of prints. Together with this reduction in time and effort is an increased economy in materials.

Although specific materials and operational techniques are set forth in the above exemplary embodiments using the developing materials and techniques of this invention, these are merely intended as illustrations of the present invention. There are other materials and techniques than those listed above which may be substituted with similar results. Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure which modifi- 1 1 cations are intended to be included within the scope of this invention.

What is claimed is: V l. The method of making an imaging master capable of producing multiple prints comprising the steps of 5 forming an electrostatic latent image on an insulating recording member, developing the electrostatic latent image with a liquid developer comprising an electrically insulating liquid having an electrical resistivity greater than about ohm-cm. and having dispersed therein l. finely divided,.substantially colorless, polypeptide material capable of readily imbibing an aqueous solution of a water-soluble dye, said polypeptide being attractable to said latent image, and

2. colored pigment particles, said pigment particles being present in an amount of from about 1% to about by weight of the polypeptide image to the recording member.

2. An imaging method comprising the steps of:

a. forming an electrostatic latent image on an insulating recording member;

b. developing the electrostatic latent image with a liquid developer comprising an electrically insulating liquid having an electrical resistivity greater than about 10 ohm-cm. and having dispersed therein l. finely divided, substantially colorless, polypeptide material capable of imbibing an aqueous solution of a water-soluble dye, said polypeptide being attractable to said latent image, and 2. colored pigment particles, said particles being present in an amount of from about 1% to about 20% by weight of the polypeptide material; c. fixing the polypeptide image to the recording member; d. contacting the polypeptide image with an aqueous solution of a water-soluble dye to permit the polypeptide image to absorb the dye; e. removing excess dye solution; f. contacting the polypeptide image having absorbed dye with a dye transfer receiving surface to transfer dye to the receiving surface in image configuration; g. repeating steps (d), (e) and (f) at least one additional time. 3. The method of claim 2 wherein said insulating recording member comprises a zinc oxide binder composition and wherein the zincoxide particles are removed from the recording member before step (d).

4. The method of claim 2 wherein said polypeptide material is gelatin. 

1. FINELY DIVIDED, SUBSTANTIALLY COLORLESS, POLYPEPTIDE MATERIAL CAPABLE OF READILY IMBIBING AN AQUEOUS SOLUTION OF A WATER-SOLUBLE DYE, SAID POLYPEPTIDE BEING ATTRACTABLE TO SAID LATENT IMAGE; AND
 2. COLORED PIGMENT PARTICLES, SAID PIGMENT PARTICLES BEING PRESENT IN AN AMOUNT OF FROM ABOUT 1% TO ABOUT 20% BY WEIGHT OF THE POLYPEPTIDE IMAGE TO THE RECORDING MEMBER.
 2. colored pigment particles, said pigment particles being present in an amount of from about 1% to about 20% by weight of the polypeptide image to the recording member.
 2. An imaging method comprising the steps of: a. forming an electrostatic latent image on an insulating recording member; b. developing the electrostatic latent image with a liquid developer comprising an electrically insulating liquid having an electrical resistivity greater than about 1010 ohm-cm. and having dispersed therein
 2. colored pigment particles, said particles being present in an amount of from about 1% to about 20% by weight of the polypeptide material; c. fixing the polypeptide image to the recording member; d. contacting the polypeptide image with an aqueous solution of a water-soluble dye to permit the polypeptide image to absorb the dye; e. removing excess dye solution; f. contacting the polypeptide image having absorbed dye with a dye transfer receiving surface to transfer dye to the receiving surface in image configuratIon; g. repeating steps (d), (e) and (f) at least one additional time.
 3. The method of claim 2 wherein said insulating recording member comprises a zinc oxide binder composition and wherein the zinc oxide particles are removed from the recording member before step (d).
 4. The method of claim 2 wherein said polypeptide material is gelatin. 